CA2100723A1 - Transponder Location and Tracking System and Method - Google Patents

Abstract

A transponder location and tracking system (100) having a phased array antenna (102, 104) mounted at a toll collection station includes a plurality of antenna array elements (112, 114, 116, 118, 120, 122) for receiving a signal from a transponder (106) mounted on a vehicle and for providing a plurality of antenna element electrical signals. A plurality of phase detectors (140, 142) are provided for comparing the phase of the electrical signals to provide a plurality of phase difference signals. A plurality of angle-of-arrival calculation processors (141, 143) is provided for converting the phase difference signals to spatial signals to define the angles-of-arrival of the vehicle transponder signal. A position calculation processor (144) is included for providing an output signal representative of the location of the vehicle in response to the defined angles-of-arrival. In a preferred embodiment, the transponder location and tracking system (100) includes a plurality of receiver processing devices (107, 108) for amplifying and filtering the electrical signals from each antenna element. The phase detectors (140, 142) then compare the phase of the electrical signals to a reference element signal. Each phase detector (140, 142) provides a digital representation of the phase difference signals.
The spatial signals represent the angle-of-arrival of the vehicle transponder signal. The position calculation processor (144) operates on the spatial signal to determine the vehicle transponder position. A tracking mechanism (154) is provided to plot the location of a moving vehicle along the roadway.